1. Field of the Invention
The invention relates to a dowel for securing objects to construction elements, in particular gypsum plaster boards, with an expandable dowel body which has an inner bore into which a fastening screw can be screwed. At an insertion front area, the dowel body is subdivided into at least two head segments by slots starting at a front end and has at the front area along the outer surface a continuous necking. At the rear end opposite to the front end, the dowel body includes a stopping plate extending transversely to a dowel longitudinal axis.
The invention also relates to a method for making a dowel with an inner bore and an inner thread.
2. Description of the Related Art
From U.S. Pat. No. 3,869,959 there is known a dowel for securing objects to construction elements, in particular to gypsum plaster boards, with a spreadable dowel body which has an inner bore into which a fastening screw can be screwed, wherein the dowel body is subdivided into at least two head segments by slots starting at a front end and includes at the front area along its outer surface a continuous necking, and wherein the dowel body at the rear end opposite to the front end includes a stopping plate extending transversely to a dowel longitudinal axis.
The dowel known from U.S. Pat. No. 3,869,959 is made of a uniform dowel body with a cylindrical section which corresponds to a bore in the construction part to which the dowel is to be secured. At the rear end of the dowel body, there is disposed a threaded inner bore and a stopping plate. At the rear area opposite to the front area, the dowel body has a collar which is connected with the rear area through a conical necking. At the front area, the dowel body has a plurality of slots which can spread radially when a fastening screw is inserted in the inner bore. On the circumference of the dowel body there are arranged a plurality of ribs for preventing rotation of the dowel in the dowel bore. With the known dowel, the fastening screw can disadvantageously be pulled out of the inner bore when tensile forces are applied along the longitudinal axis of the dowel. To making it more difficult for the fastening screw to be pulled out, the known dowel has to be provided with a relatively coarse thread which makes it hard to turn the screw. The dowel may disadvantageously also rotate together with the fastening screw when the fastening screw tightened. To counteract this situation, additional ribs are provided on the circumference. These ribs, however, can damage the construction element surrounding the dowel.